The object of the proposed investigation is to gain additional insights into the molecular events and regulatory mechanisms involved in the alterations of cell structure and function during the mammalian cell cycle, particularly the mitosis to G1 transition. Synchronized HeLa S3 cells and adenovirus type 2 transformed rat embryo cell lines will be employed in these investigations. Aspects of nuclear reformation at the completion of mitosis will be investigated by asking specific questions concerning the synthesis, fate and structural relationships of specific nuclear matrix polypeptides. Incorporation of lipid precursors into the nuclear envelope as it reforms is being visualized by electron microscopic autoradiography and by biochemical procedures. The post-mitotic survival of messenger-RNA is also being examined. This type of information should elucidate more information in cultured human cells concerning the biochemistry of macromolecules and their re-association to establish the interphase state at the completion of mitosis.